Re: [Vala] use weak and var together

[Yu Feng <rainwoodman gmail com>]

Hi Jurg,

Sorry for digging such an old post but I discovered something. See the
end of the message.

On Fri, 2008-12-12 at 08:08 +0100, Jürg Billeter wrote:
> On Thu, 2008-12-11 at 23:56 -0500, Yu Feng wrote:
> > On Thu, 2008-12-11 at 22:11 +0100, Jürg Billeter wrote:
> > > On Wed, 2008-12-03 at 14:05 +0000, Frédéric Gaudy wrote:
> > > > I don't know if it' a bug or a feature. When I use weak and var
> > > > keywords, I obtain a error:
> > > > error: The type name `var' could not be found
> > > >
> > > > Code : 
> > > > weak var thread = Thread.create( this.process_thread, true);
> > >
> > > I haven't decided yet whether we should support that and if yes, what
> > > exact syntax to use. In addition to your example, just
> > >
> > >   weak thread =...
> > >
> > > might also be a possibility. I tend to not support it at all at the
> > > moment and rather try to minimize the number of situations where 'weak'
> > > is needed.
> >
> > I am wondering why you dislike weak so much. It does usually mess stuff
> > up but it is also good if one knows what she is doing.
> > It not only saves a ref and unref, but also breaks circular references. 
>
> var is only used for local variables and you never need to break
> circular references with local variables. I only dislike it if it's used
> to workaround issues with not reference-counted objects. weak is
> perfectly fine to break circular references, that's the main reason it
> exists.
>
> > Talking about circular references, is it possible to have a circular ref
> > breaker mechanism like the one in GTK for vala fundamental classes?
>
> I don't think we should always add a dispose mechanism to fundamental
> classes. However, if someone wants to use that, it should still be
> possible to implement this with a bit of extra Vala code.

I suddenly realized it is impossible to write dispose mechanism with
extra vala code because one can not override the hidden unref method,
therefore one can not do the cycle detection/breaking at the right time.

Yu
> Jürg